The present invention is directed in general to an apparatus for connecting a radio to one or more accessory devices, and more specifically, to such an apparatus providing a reliable, robust, repeatable, waterproof and quick release interconnect.
Various types of personal radio systems, which necessarily include a portable receiving unit, are now commonplace. In some systems, the portable radio may comprise a transceiver for providing two-way communications between two individual users or between a single user and a group of other users. A base station or repeater receives a signal from the calling unit and re-transmits the signal to one or more called units.
A trunked radio repeater system is one such personal radio system in widespread use today. In the trunked system, a pair of radio frequencies is assigned to a group of public service users, such as a fire department, police department, or emergency service providers. Each radio frequency group includes an inbound working channel for carrying traffic from a user to a base station or a repeater, and an outbound working channel for carrying communications traffic from the repeater to the intended recipients. Each user is equipped with a portable transceiving unit, typically referred to as a portable radio, for communicating with members of his or her group. Generally, the portable radios are hand-held or received within a harness assembly strapped to a user so that the radio is readily accessible. The portable radio may also be temporarily stored in a pocket of the user""s clothing, set upon a work surface, or used within a vehicle.
When a user initiates a call, the trunked radio system assigns a frequency pair (including an inbound working channel and an outbound working channel) to the call. Once the call has been set up, the calling party talks into the portable radio or into an accessory microphone connected to the portable radio. The voice signal is sent to the base station over the inbound working channel and then broadcast to all members of the calling party""s group over the outbound working channel.
It is common practice for the radio to have a multi-pin electrical connector accessible at an external surface of the portable radio unit. A number of accessories can thereby be connected to the portable radio so as to become an integral part of the radio system. Certain of these radio accessories offer the user an opportunity to enjoy hands-free operation of the portable radio. Other accessories provide remote control operations and/or functions that may not be available within the basic portable radio. One accessory that facilitates hands-free operation is a remote speaker/microphone. The remote speaker/microphone is typically worn on the user""s shoulder and connects to the portable radio through a cable and connector, while the portable radio remains attached to the harness assembly by or near the user""s belt. The remote speaker/microphone brings a majority of the basic radio functions to the user""s shoulder, for example, a push-to-talk button by which the user can activate the portable radio to place a call. When use of the radio is transitioned to the vehicular environment, the remote speaker microphone and related accessories can be disengaged from the portable radio at the multi-pin connector, followed by the engagement of a different accessory device for interfacing with one or more related systems within the vehicle, such as a power supply for recharging the portable radio battery, a speaker mounted within the vehicle, and a microphone also mounted within the vehicle. Depending upon the preferences of the user, accessory devices may be changed as the portable radios are swapped from one user to another. Frequent swapping, with attendant changes in accessory devices, to fatigues the interconnect system.
Typically, the portable radio user is engaged in public safety matters, such as a police offer, fire fighter, or ambulance personnel. The radio is therefore often subjected to extreme environments, such as high-pressure water flows and high stress scenarios where reliable and immediate availability of the portable radio, including proper functioning of the connector of the present invention, is extremely critical.
As discussed above, the portable radio is generally received within a harness and given the size and bulk of the radio, it is usually only semi-rigidly attached to the operator. The cord leading from the accessory device terminates in a multi-pin connector for mating with the connector of the portable radio. When the accessory speaker/microphone is mounted to the user""s shoulder, the cord typically runs along the operator""s body, generally from the waist to the shoulder. In the prior art, the accessory cord connector is a moderately large protrusion extending from the side of the radio when mated thereto. It is commonly bumped and subject to jarring forces from many directions during use. For instance, mechanical damage occurs most often when the user enters or exits a vehicle, door or arm chair while wearing other equipment or gear. The cord easily becomes tangled as a fire fighter crawls along a debris-strewn floor or through a small passage, or while a police officer is chasing a fleeing criminal. In short, any time the connector body comes in contact with an immovable object, it is generally the former that is damaged.
In one prior art embodiment, the accessory connector is removably attached to the portable radio by a single screw penetrating through the connector and mating with a threaded hole in the portable radio body. See for example U.S. Pat. No. 4,792,986. It is common practice for users to over tighten the screw in an effort to maintain a waterproof seal at the connector interface. Under emergency and stressful conditions, it can prove difficult to accurately align the connector (12 pins in one embodiment) with the mating holes and then actuate the screw to tighten the connector in place. Over-tightening the screw can cause it to shear, requiring replacement of the connector and perhaps a repair of the portable radio if the broken screw remains lodged in the mating screw hole. Under-tightening the connecting screw provides poor electrical connection between the connector halves.
To prevent connector misalignment during the connecting process and while in use, certain field modifications have been attempted, including the use of metal straps and hooks to hold the connector to the portable radio. The metal straps frequently snag on the user and deform out of shape. The plastic hooks eventually wear out and require replacement. In extreme situations, the prior art connector is bonded to the portable radio to prevent connector movement relative to the portable radio. These attempted prior art modifications render it difficult, and in some cases impossible, to disconnect the portable radio from a first accessory device, for instance the speaker/microphone device, and connect it to a second accessory device, for example, vehicular accessories.
Referring to the patent mentioned above (U.S. Pat. No. 4,792,986), a threaded knurled knob is used as the single point of attachment between the connector and the portable radio body. It is known that a single screw cannot prevent rotational movement of the connector relative to the portable radio Rotation through any angle greater than approximately 15 degrees causes loss of electrical connection between one or more of the contacts. If the mating electrical contacts comprise pins and mating holes, such rotation of the connector can cause bending of the pins, or in extreme cases, breaking of one or more pins. In an effort to prevent these occurrences, and under the belief that tighter is always better, users will tighten the screw as tight as possible. As mentioned above, in extreme cases the screw will shear under the extreme forces imposed upon it.
In addition to a relatively quick release electrical connector for the purpose of changing between various accessory devices such as those worn by an individual user to those carried in a vehicle, it should also be noted that certain features of the radio can be programmed through use of yet another accessory device. As explained in detail in U.S. Pat. No. 4,792,986, the portable radio senses the resistance or impedance between specified pins of the electrical connector (or between a specified pin and ground) and in this way determines the nature and function of the accessory to which the portable radio is connected. In response to the measured impedance value, the internal computer-controlled circuits of the portable radio automatically reconfigure the portable radio mode of operation. As discussed in the aforementioned patent, one of the unique resistance values identifies an external controller for reprogramming certain internal functions of the portable radio. Another unique resistance value identifies the external speaker/microphone as the accessory device connected to the portable radio. Yet another resistance value identifies the vehicular accessories.
As discussed above when the accessory connector is not tightly mated with the portable radio, rotation of the accessory connector relative to the radio body can change the resistance value or break the electrical connections between contacts. In the event the sensed resistance value changes, the portable radio will switch operational modes, although the same accessory device remains attached to the portable radio. If the operative contacts to the attached accessory device are instead broken, while the sensed contacts remain intact and with no change to the measured resistance value, the portable radio will continue to operate as though the speaker/microphone is attached. As a result, the radio controller mutes the speaker within the radio body, rendering the entire unit useless, (assuming there is no provision for manually activation of the radio speaker).
The above-mentioned disadvantages associated with prior art connectors are overcome by the improvements offered by a connector constructed according to the teachings of the present invention. The connector includes a top catch or slot for engaging a mating tab on the portable radio. Once engaged, the connector is rotated downwardly into place, using the mated slot tab assembly as the pivot point. A quarter turn screw on the connector engages a mating receptacle on the radio and is then rotated to firmly secure the connector to the portable radio.
The mechanism of the present invention provides several advantages over the prior art connector arrangements. In particular, a connector constructed according to the teachings of the present invention offers additional strength and impact resistance to the connector, overcoming problems created by rotation of the connector when it is bumped against an immovable object. Use of a quarter turn screw serves as an indicator to the user that the screw has been properly tightened, and that no further tightening is required. Further, the use of a screw device that has only two positions, a tightened position and an untightened position, (a so-called xe2x80x9cbinary screwxe2x80x9d) avoids any mistake on the user""s part that the screw is either too tight or too loose. The mating tab/slot arrangement prevents misalignment of the electrical contacts (e.g., mating connector pins and holes) during the connection process and also during use. Since there are two attachments points between the connector and the body of the portable radio, rotation of the connector relative to the portable radio is precluded.
Water intrusion to the electrical contacts is avoided through the use of a waterproof seal surrounding the contracts and further surrounded by a skirt integral to the connector body. Without a skirt surrounding the seal, water can hammer beyond the seal into the contact area, shorting contacts or changing the resistance value that determines the type of the accessory connected to the portable radio. Finally, since the portable radios are widely used by emergency and public service personnel, it is critical to have a connector providing a quick release mechanism for connection and disconnection.